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W. P. HORTON, Jr.& AyB; JONES.

METHOD or AND APPARATUS FOR OBTUNDING NERVES. 53559051.. Patented Mar. 19, 1895. Y

.WTNESSESL mmvrozzsw To allwhom-it md fconcerma Be it known. that we, WILLIAM F; Hoar'on,

of the United .St'ateajaesidi-ngat Cleveland, ini the 'couutyof (JuyahogaangiState ofQhimhave' invented a-M 'thodof and Appaixratus 'lor'gOgb eT-ceth Durv ing ,the Excavation ,off' Cavities; and: we -cloj'. l hjerebydeclare the-following to bee fnllgcl 'ear of the patients face 'on which the tooth to he carrying-our-process into eflr'ecu'appliei in WILLIAM I", non'romsa, AND Assur stones, oh oLEvnL-ANI'), on o -sA D HORTON AS QRL To WILLIAM 5P. Homes, on SAME ,rLAeE.

.MsT -io o ;for D ,APPAATUS' tea: oksrunomc Eaves,

'senorFr'clmuour amiss part ofn tt'e 'sete t No. 535,905; dated rah 1 9, ices;v

, application sentinel, 1593, smart, 468,59 on m'ndel-l In, and" ANS'EL B.- Joltns'citizens tundina h euse y-Nsr f 19 amlexact descripticnlof the invention, such as-,will'* enable.fothers: skillediin ithe' art to whiehit appertainsto niake anduse the same,

our-invention rel'alt'e';8f to 'aprocess or ob:

winding he sensory:

following steps :-'-.first, in applying to that side excavated islocatell', San electrodelwhich is connected with one pole of anelectrical genso orator second,- inconnecting the excavating instrument with the" other pole of said genorator; .third,,in varying the external resis- -t-ance in the circuitjdnring the operation, substantially as hereinafter described. v y

" I The-qrawing representsl-the'apparatus for the manner;hereinafter-described.

a In carrying'ont our; process, we commonly employ the current generated by ,a single cell battery, but we have in our experiments and operations, :found .casesfwhere the current from as many as four cells was necessary.

- An electrode A, connectediwith one pole of the generator B, (preferably-the negative pole) is securecl by means ota rubber-strap a, or'by any'snitable mean's,'to--that side of the patients face on'irhichthe tooth to be excavated I is located; The other pole of the generator is electrically connected with the excavating o instrument G. 'Inihe. rnod'ern practice ofdengtistryjthe excavator is generally a revoluble ,burrdri'ven by a dental engine. Care must be exercised to1con1pelthe passage of the current f'romthe'excavator to the electrode A throughthe tooth.- To secuz etliis result, it is best to form the'hand piece ofthe excavator of some insulating material; and the excavator shouldbeso used that there is noelectrical connection between it antl'any 5'o other part of the vpatient than the tooth. l

The reason for preferring to connect the e v I nerves of a tooth during the excavation thereofiand it consists in the.

" elect-rodeA with the negative pole is as fol I lows: One source of the pain experienced by the patient is'due to .the'lacerationof the nerve statesmen the-tnbuli which ramify; 5 the-dentine. Another source of pain is the heat generated by the revolution of the burr." ,Now, this found that in passingan electrical burrenl; through the human body, heat isgenqerated atthenegativeelectrode. Therefore,

iii-order that the pain due to the heat generated nedessarily byth'e burr shall not be f-increaseti by the. heat due to the electric can rent, we prefer to connect the electrode A with Jthe negative pole as stated. 6 5' The teeth are supplied by nerves which I originate in the fifth cranial nerve. Branches A of the fifth nerve of the cranium pass from the cranial cavity through channels in the superior or sub-maxillary bones; and being sub-divided, enter the several teeth, wherein they are again sub-divided, forming the mi- .nute nerve filaments which ramify the den tine. The parts of the nerve in the teeth and in the channels in the bone, are therefore more or less boinpletely insulated (electrically) from eacj other, as. well as fromother parts i of the anatomy; so that'a current of electric- "ity introlluced into a tOOflLIIlllSi; pass with comparatively little loss over the nerves as conductors into the cranial cayity. The shortest route for the escape of the currenttherefrom, is through the foramina in the skull, through which pass other branches of the fifth nerve to'supply the face. In order. therefore, l

to pass over thesensory nervesof a tooth, an electrical current which will meet with aslittie resistance from the body as possible, we place one electrode as before stated, against thejside of the face just in front of the lower 90. lobe of the ear. By placing theelectrocle here, there is not only the least possible resistance in the body, but there is also thelcast variationinthe resistance in different patients.

Our theory with respect to the process is 5 substantially as follows, viz: that in anygiven individuah'it is necessary to pass over each of the filaments which are aficcted by the operation, some certain quantity of current. We are unable to express in the terms em- 10o ployed in electrical measurement, what quantity of current is required, for several reasons,

viz: first, we have been unable to measure the entire quantity which passes through a patient by any instrument which we have beeil able to obtain; second, it is impossible to determine how much the currentissub-divided in its passage through the dental filaments; that is to say, to determine what part of the entire quantity employed passes over any one filament. This quantity, moreover, differs in different individuals, this differencebeing apparently dependent on differences in what, in common parlance, is known as the sensi tivencss of the nerves. Perhaps a more accurate statement of the causes of these differences is this, viz: that the teeth of some persons contain more nerve filaments than others, which filaments are placed more closely together. Another cause of the personal differences maybe the -fact, that owing to differences in the structure of the teeth and bones, the nervesare more completely insulated electrically in some persons thanin others. Now, it is possible that the theory above outlined may be incorrect, but we have found it entirely consistent with the acts necessary to be done in order tobe practically successful in excavating teeth by the described process without. pain.

In order to vary the quantity of current to compensate for the varying conditions which arise in practice, it is necessary to connect into the circuit a resistance box by means of which the operator may vary the external resistance, that is to say, the resistance external to the body. We have foundin practice that a resistance box, capable of introducing about fourteen thousand ohms resistance, by increments of one hundred ohms, is a suitable box for the purpose. In the drawing, this resistance box is represented by D. It is un-, necessary to describe in detail the construction of the box. It is provided with two switches, d and d, which are adapted to engage with any one of the contact points, 1', 2, 3, &c., and 13, 14, &c., respectively. When switch d touches the contact point 1 and switch d touches contact point 13,- the box introduces into the circuit approximately fourteen thousand ohms resistance. As the switch is moved up into contact successively with the contact points 2, 3, 4, &c., the resistance is reduced approximately one thousand ohms for each point. When the switch (1 is moved successively into contact with the points 14:, 15, the, the resistance is reduced approximately one h u'nd red oh ms for each point.

As before stated, the quantity of current required difiers in different individuals, and it also differs in different teeth of the same person, 'and even at different periods in the excavation of the same tooth.

. In conducting operations according to the process,'we prefer to beginanoperation when the switches d and d are in engagement with the points 1 and 13,--that is to say, with as much resistance in the circuit as can be inssiaeoe -If the quantity of current is insufficient, the

patient will feel a sensation in the dental nerves attected by the revolution of the burr. 'lhe first sensation will not,if the operator is watchful and careful, be one of pain. It will resemble the sensation produced by touching an external object to the hand. The operator now reduces the resistance by the movement of the switch (I from point 1 to points 2 little heat is developed.

or'3 and so on, trying the current carefully after each movement, nntil the operation may he proceeded with without producing any sensation in the dental nerves. To attain this result, it may be necessary to move the switch d by which the resistance may be changed by incrementsof one hundred ohms. It is not necessary to proceed in the described manner in each case, there is then comparatively little danger thereby of employing toov strong a current, which might injure the nerve, or might produce even greater pain than would result from the excavation of the cavity without any current.

The operator may be guided in the practice of the process as above set forth, er in proceeding more directly in the application of the proper quantity in any case'by the following facts: In removing what is commonly called white decay, aless quantity of current is needed than in any other eperatiou -b ecause the decayed matter is sofuwhereby the burr, and further, because the burr does not come in direct contact with any live filament. in removing the so-called leathery tissue, a greater quantity of current is required, for the reason that the under side of this leathery patch: enters numerous tnbuli in the tooth, whereby all the'filaments in said bythe revolution ofbut we preterit because tubuli are affected inoreor'less by the workin g of the burr in said. tissue. ca-yed substance has been removed, and the burr is acting on the healthy dentine, either for the purpose of thoroughly cleansing the cavity, or for drilling the retaining points for the filling, a still greater quantity of Y current is required. In drilling into the dentine, it isfound that the quantity of current required is greater as the said de'ntine is harder, because more heat is generated by the revolution of the burr in hard dentine than in soft dentine. Care must be taken to prevent the burr from touching any other part of the tooth than that at. which the drilling is in progress, because by such touching a part of the current is divided from the filaments When all of the de- 7 re .a quantity of electricty which results from the-em loymen't of 5 triclt whlch'results from one co intro notion of approximately seven thou- 5 5 method and apparatus having for their object 5 thequantity of current must be-increased. 7

re mately four thousand ohms I understood that :5 statement impossible.

go is sufficient.

3 5 times, though seldom,

side of the patients face on which a tooth is located, said toothmay be excavated without an electric current is passed into said tooth from the excavating instrument. 5 going directions are merely suggestions, as exfore been made to obtund the nerves of a tooth the PatentjNo. 22,851, granted February 8,

69 method,

satisfactory results. To be successful, we

which are being lacerated or otherwise affected by the operation. -11, however, the cavity is so situated that to impossible to avoid touching thesidc walls,

' In a crating under the differentconditions name we have found that, in the average case, white decay may .be removed without pain to the patient by the use as described-of a single cell and the in troduc ion of approximately ten thousand ohm's external resistance into the circuit; to remove leathery tissue, a qnantitiy'of elecl and the sand ohms external resistance. For drilling .into the healthy de ntine, a current having the same electro-motive force and approxiresistance will often produce the desired result. Itwill be these figures are only approximate. The verygreat differences in personal characteristics render a more exact.

We have heretofore recommended that a current of small quantity be employed at the beginningof an op ration, and that the quantity be gradually increased by reducing the resistance,until it The above figures may guide the operator by informing him of the points at which he may ordinarily expect to be successful. It sometimes happens, however, that a less quantlty'will be suiiicient. It somehap ens that anelecexcavate it, it is tro-motive force of two, three or even four cells will be required. 4

The essential iieature of the discovery is this, .viz: that if one electrode be placed against one pain to the patient if the proper quantity of plicit as the nature of the case will permit, as

to the best method of determining the proper quantity of current required.

We are aware that attempts have heretoduring the excavation thereof, by means of an electrical current. We are aware also of 1859, to W. G. A. Bonwell, which describes a this result, but ,we do not intend that our claim shall include theprocsedescribed by Bonwell suggests that one electrode -be heldin one hand. Wehave tried this but have been unable to secure any find it-necessary to apply one electrode to that side of'the face on which the tooth is located.

'tion, substantially as specified. a The fore- 3 This makes it possibleto send over the dental nerves the proper quantity of-cur-rent of an intensity not too great to be effective.

'Bo'nwell suggests that the power of the current he graduated so as to be-just strong enough. This statementbegs the question, for it gives no information as to the manner as to the principles which should govern in graduating it. inbefore described what quantity of current approximately is required, and the principles which should govern the operator in changing the external resistance in the current so that the desired result shall be obtained under the varyingcondition's which arise in practical work. We intend that our claims shall be limited to include the doing of those things the necessity for which we have discovered.

, in which'the current should he graduated nor We have discovered and here- Having described our invention, we claim- 1. The herein described process of obtunding the sensory nerves of-a tooth during the excavation of a dental cavity therein, which consists in (first) applying to that side of the patients face on which the tooth is located, an electrode which is connected with one pole of an electrical generator, (second) connecting th pole of said generator; and (third) varying the current outside the body of the patient, substantially as and for the purpose specified.

2. The herein described process ofobtundlug dental nerves during the excavation of a tooth, which consists in (first) applying -to that side of the. patients face on which the tooth to be excavated is located, an electrode which is connected withthe negative pole of a galvanic battery;. (second) connecting the excavating instrument with the positive pole of saidgenerator; and (third) varying theresistance in-the circuit outside of the patient during the progress of the excavating operaand for the purpose In an apparatusjor excavating dental cavities and simultaneously ohtunding. the sensory nerves which are being alfected by the operation, the combination of an electrical generator,an electrode connected with one pole of said electric generator, and means for securing the same against the with the revolving burr of adentalengine havingan insulatinghand piece, suitable electrical "connections between said burr and the other pole of said battery, and means for varying the resistance in the circuit by small increments, substantially as and for the purpose specified. I

In testimony whereof-we aflix our signatures inpresence of two witnesses.

WILLIAM F. \I-IORTON, JR. i ANSEL B. JONES. "Witnesses:

E. L. THUns'roN, 0. T; J ONES.

e excavating instrument with the other patients face, 

